This invention relates to a hand control system for power hand tools. More specifically, the invention is directed to a hand control system for dental drive and medical or surgical drive systems.
There are numerous types of control systems for power tools such as dental drive and medical and surgical power tools. In such a prior art system, there are several basic functions which may be performed. These include providing a supply of air, water or other gaseous and liquid mediums and controlling the operation of a tool member.
More particularly, the control system of this invention is used in power tools having a hand-piece unit. The power tool may include a rotatable tool member mounted in the hand-piece unit and an air driven motor for rotating the tool member. In a dental device, the hand-piece unit includes a drill bit chuck, belt and pulleys to rotate the drill bit chuck or an air driven vane type motor assembled to a tubular, pencil-type handle. The tool members may comprise drill bits, rotary saws, rotary files, grinding wheels and the like. Tool members are mounted on the hand-piece unit to perform various functions related to the dental or medical professions.
Various types of control systems are used in the prior art to operate the various functions of the power tool. The most common type of control system comprises a foot-actuated control valve which regulates the amount of air and/or water to be supplied to the hand-piece unit. This water or air supply operation is accomplished either by pressing an air control foot pedal and/or a water control foot pedal of the foot-actuated control mechanism. Prior art dental or medical drive cabinets include various types of components such as air and water filters, metering valves, gauges, and related apparatus that provides the interconnection between the incoming supply air and water, the foot-actuated control valve assembly, the hand-piece unit and water syringe.
It is also known in the prior art to use hand control systems for power hand tools having a hand-piece unit. These known hand control systems, however, simply include an on-off switch. There is no particular type of circuit means for sensing a low current electric signal which is activated by a control means to provide a higher current operational signal to actuate the operation of the power tools.
In one such prior art hand control mechanism disclosed in U.S. Pat. No. 3,346,958, the operator of the hand-piece unit touches a recessed button located thereon. The operator's hand itself acts as a path for the current which completes the circuit back to the electrical system thereby actuating the various operations of the power tool. This particular system has many disadvantages such as not being able to offer a finger-tip controlled, modulated system for varying the speed of the tool members. Furthermore, there is no possibility of the use of a separate switching control assembly which may be attached to existing hand-piece units. It is further noted that where speed control is desired, the foot control system is used instead of relying upon a manually operated mechanism.